Hi again
First of all I think it is easy to improve the assess/evaluate feedback. I know this is something everyone recommends but not many people actually do it, but I underline the key words and write a brief plan. This really helps especially for extending response questions, because if I just start writing I tend to waffle on and miss important bits of information, whereas if I think about my answer as a whole before I start writing my answer is a lot more succinct and relevant (this links to your feedback of not relevant). Another tip my teacher gave us is to write a sub-heading for "judgement" in assess or evaluate questions, which reminds you to include a judgement and also makes it obvious for the marker.
For not being specific enough, I think it's just a matter of practicing and knowing your content really well, and
making sure you mark or get someone else to mark your practice questions. You seem to already be doing this, but I have improved so much by getting my teacher to mark a ton of practice questions for me (she is a really harsh marker so it forces me to be even more specific).
Good luck, hope this helps!